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Amplitude growth rates of quasi-monochromatic gravity waves were estimated and compared from multiple instrument measurements carried out in Brazil. Gravity wave parameters, such as the wave amplitude and growth rate in distinct altitudes, were derived from sodium lidar density and nightglow all-sky images. Lidar observations were carried out in São Jose dos Campos (23 ∘ S, 46 ∘ W) from 1994 to 2004, while all-sky imagery of multiple airglow layers was conducted in Cachoeira Paulista (23 ∘ S, 45 ∘ W) from 1999–2000 and 2004–2005. We have found that most of the measured amplitude growth rates indicate dissipative behavior for gravity waves identified in both lidar profiles and airglow image datasets. Only a small fraction of the observed wave events (4% imager; 9% lidar) are nondissipative (freely propagating waves). Our findings also show that imager waves are strongly dissipated within the mesosphere and lower thermosphere region (MLT), decaying in amplitude in short distances (<12 km), while lidar waves tend to maintain a constant amplitude within that region. Part of the observed waves (16% imager; 36% lidar) showed unchanging amplitude with altitude (saturated waves). About 51.6% of the imager waves present strong attenuation (overdamped waves) in contrast with 9% of lidar waves. The general saturated or damped behavior is consistent with diffusive filtering processes imposing limits to amplitude growth rates of the observed gravity waves.
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A new approach to characterizing medium-scale gravity waves using Antarctic airglow observations
Abstract. Medium-scale gravity waves (MSGWs) are atmospheric waves with horizontal scales ranging from 50 to 1000 km that can be observed through airglow all-sky images. This research introduces a novel algorithm that automatically identifies MSGWs using the keogram technique to study the waves over the Antarctic Peninsula. MSGWs were observed with an all-sky airglow imager located at the Brazilian Comandante Ferraz Antarctic Station (CF, 62° S), near the tip of the Antarctic Peninsula. Several preprocessing techniques are necessary to extract the parameters of MSGWs from the airglow images. These include projecting the images into geographical coordinates, applying a flat-field correction, performing consecutive image subtraction, and employing a Butterworth filter to enhance the visibility of the MSGWs. Additionally, a wavelet transform is used to identify the primary oscillations of the MSGWs in the keograms. Subsequently, a wavelet transform is also used to reconstruct the MSGWs and obtain the fitting coefficients of phase lines. The fitting coefficients are then used to calculate the MSGW parameters and assess the quality of the results. Simulations with synthetic images containing typical propagating gravity waves were conducted to evaluate the errors generated during the MSGW calculations and to determine the threshold for the fitting parameters. This methodology processed a year's worth of data in less than 1 h, successfully identifying most waves with errors lower than 5 %. The observed wave parameters are generally consistent with expected results; however, they show differences from other observation sites, exhibiting larger phase speeds and wavelengths.
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- Award ID(s):
- 2327914
- PAR ID:
- 10650473
- Publisher / Repository:
- Atmospheric Measurement Techniques
- Date Published:
- Journal Name:
- Atmospheric Measurement Techniques
- Volume:
- 18
- Issue:
- 21
- ISSN:
- 1867-8548
- Page Range / eLocation ID:
- 6345 to 6360
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.5194/amt-18-6345-2025
